1. Technical Field
The present invention relates to a metal interconnection structure and a method of forming the same, and more particularly, to a metal interconnection structure in which formation of voids in a via contact are prevented and a method of forming the same.
2. Description of the Related Art
In order to achieve high speed semiconductor devices, copper has been used more prominently than aluminum as a interconnection material. Since aluminum has a specific resistance of 2.74 μΩ-cm while that of copper is 1.72 μΩ-cm, a semiconductor device which employs copper interconnections has a higher performance than a semiconductor device having aluminum interconnections. Moreover, copper interconnection can be used with an inter-metal dielectric layer having a low dielectric constant since a copper interconnection can be formed at a low temperature, thereby remarkably reducing RC delay. However, forming a copper interconnection pattern is more difficult than forming an aluminum interconnection pattern because etching copper is more difficult than etching aluminum. However, this problem has been substantially solved by using a damascene process.
To form a copper interconnection using a damascene process, an inter-metal dielectric layer pattern and an inter-layer dielectric layer pattern are sequentially formed on a lower copper interconnection layer. The inter-metal dielectric layer pattern has a via contact hole that exposes a portion of the lower copper interconnection layer, and the inter-layer dielectric layer pattern has a trench that exposes the via contact hole. In this state, a barrier metal layer is formed, and then a copper interconnection layer, is formed to completely fill the trench and the via contact hole. After performing a planarizing process, an upper copper interconnection layer is complete.
However, in the damascene process for forming a copper interconnection, stress is generated in the copper interconnection due to shrinkage caused by thermal stress and crystal growth. This stress may not be a severe problem when the width of the upper copper interconnection layer is narrow, that is, when there are few vacancies within the upper copper interconnection layer. However, when the width of the upper copper interconnection layer is large, that is, when there are many vacancies within the upper copper interconnection layer, voids or vacancies are formed in the via contact hole due to a stress gradient. The vacancies within the upper metal layer gather by diffusing through interfaces of crystals. When there are voids within the upper copper metal interconnection, the interconnection can become disconnected, thereby degrading the reliability of the semiconductor device.
Accordingly, it would be desirable to provide a metal interconnection structure in which formation of a void is prevented. It would also be desirable to provide a method of forming a metal interconnection structure in which formation of a void in a via contact is prevented by using a damascene process.
According to one aspect of the present invention, a metal interconnection structure comprises: a lower metal interconnection layer pattern disposed in a first inter-layer dielectric layer; an inter-metal dielectric layer on the first inter-layer dielectric layer and the lower metal interconnection layer pattern, the inter-metal dielectric layer having a via contact hole that exposes a portion of an upper surface of the lower metal interconnection layer pattern; a second inter-layer dielectric layer on the inter-metal dielectric layer, the second inter-layer dielectric layer having a trench that exposes a portion of the via contact hole; a barrier metal layer on exposed lateral surfaces of the via contact hole and the exposed portion of the upper surface of the lower metal interconnection layer pattern; a first upper metal interconnection layer pattern having a first thickness on the barrier metal layer, the first upper metal interconnection layer pattern completely filling the via contact hole and partially filling the second trench; a void diffusion barrier layer on the first upper metal interconnection layer pattern; and a second upper metal interconnection layer pattern that completely fills the trench on the void diffusion barrier layer.
Beneficially, the lower metal interconnection layer pattern, the first upper metal interconnection layer pattern; and the second upper metal interconnection layer pattern comprise copper.
Beneficially, the inter-metal dielectric layer is a low dielectric constant material layer having a dielectric constant less than 3.
Beneficially, the barrier metal layer is formed of at least one material layer selected from the group consisting of a tantalum layer, a tantalum nitride layer, a titanium layer, and a titanium nitride layer.
Beneficially, the void diffusion barrier layer is formed of at least one material layer selected from the group consisting of a tantalum layer, a titanium layer, and an aluminum layer.
Beneficially, the second upper metal interconnection layer pattern is at least five times thicker than the first upper metal interconnection layer pattern.
According to another aspect of the present invention, a metal interconnection structure comprises: first and second lower metal interconnection layer patterns disposed in a first inter-layer dielectric layer with a distance therebetween; an inter-metal dielectric layer on the first inter-layer dielectric layer and the first and second lower metal interconnection layer patterns, the inter-metal dielectric layer having a first via contact hole that exposes a portion of a surface of the first lower metal interconnection layer pattern, and a second via contact hole that exposes a portion of a surface of the second lower metal interconnection layer pattern; a second inter-layer dielectric layer on the inter-metal dielectric layer, the second inter-layer dielectric layer having a first trench that exposes the first via contact hole, and a second trench that exposes the second via contact hole and has a larger width than the first trench; a first barrier metal layer on inner surfaces of the first trench and the first via contact hole, and on the exposed portion of the surface of the first lower metal interconnection layer pattern; a first upper metal interconnection pattern on the first barrier metal layer, the first upper metal interconnection pattern filling the first trench and the first via contact hole; a second barrier metal layer on inner surfaces of the second trench and second via contact hole and on the exposed portion of the surface of the second lower metal interconnection layer pattern; a second upper metal interconnection layer pattern on the second barrier metal layer and having a third trench therein, the second upper metal interconnection layer pattern filling the second via contact hole and a portion of the second trench; a void diffusion barrier layer on the second upper metal interconnection layer pattern; and a third upper metal interconnection layer pattern on the void diffusion barrier layer, the third upper metal interconnection layer pattern filling the third trench.
According to still another aspect of the present invention, a metal interconnection structure comprises: a lower metal interconnection layer pattern disposed in an first inter-layer dielectric layer; an inter-metal dielectric layer on the first inter-layer dielectric layer and the lower metal interconnection layer pattern, the inter-metal dielectric layer having a via contact hole that exposes a portion of the lower metal interconnection layer pattern; a barrier metal layer formed on exposed surfaces of the via contact hole and the exposed portion of the lower metal interconnection layer pattern; a via contact that fills the via contact hole and is disposed on the barrier metal layer; a second inter-layer dielectric layer that has a trench that exposes a portion of the inter-metal dielectric layer and an upper surface of the via contact, and is disposed on the inter-metal dielectric layer and the via contact; a first upper metal interconnection layer pattern having a first thickness that fills the via contact and a portion of the trench of the second inter-layer dielectric layer; a void diffusion barrier layer on the first upper metal interconnection layer pattern; and a second upper metal interconnection layer pattern having a second thickness that completely fills the trench and is disposed on the void diffusion barrier layer.
Beneficially, the thickness of the second upper metal interconnection layer pattern is at least five times greater than the thickness of the first upper metal interconnection layer pattern.
According to yet another aspect of the present invention, a metal interconnection structure comprises: first and second lower metal interconnection layer patterns disposed in a first inter-layer dielectric layer with a distance therebetween; an inter-metal dielectric layer on the first inter-layer dielectric layer and the first and second lower metal interconnection layer patterns, the inter-metal dielectric layer having a first via contact hole that exposes a portion of the first lower metal interconnection layer pattern and a second via contact hole that exposes a portion of the second lower metal interconnection layer pattern; first and second barrier metal layers in the first via contact hole and the second via contact hole, respectively; first and second via contacts that respectively fill the first and second via contact holes, and are disposed on the first and second barrier metal layers; a second inter-layer dielectric layer that is disposed on the inter-metal dielectric layer and has a first trench that exposes an upper surface of the first via contact and a second trench that exposes an upper surface of the second via contact, a first upper metal interconnection layer pattern that fills the first trench, a second upper metal interconnection layer pattern that forms a third trench in the second trench by filling a portion of the second trench; a void diffusion barrier layer on the second upper metal interconnection layer pattern; and a third upper metal interconnection layer pattern that fills the third trench and is disposed on the void diffusion barrier layer.
According to a further aspect of the present invention, a method of forming a metal interconnection structure comprises: forming first and second lower metal interconnection layer patterns with a distance between each other in a first inter-layer dielectric layer; forming an inter-metal dielectric layer on the first inter-layer dielectric layer and the first and second lower metal interconnection layer patterns; forming a second inter-layer dielectric layer on the inter-metal dielectric layer; forming first and second trenches that expose portions of the inter-metal dielectric layer by etching portions of the second inter-layer dielectric layer; forming a first contact hole that exposes a portion of the first lower metal interconnection layer pattern in the first trench, and a second contact hole that exposes a portion of the second lower metal interconnection layer pattern, by etching the portions of the inter-metal dielectric layer exposed by the first and second trenches; forming a barrier metal layer on inner surfaces of the first trench, the second trench, the first contact hole, and the second contact hole, and on exposed surfaces of the first and second lower metal interconnection layer patterns; forming a first upper metal interconnection layer on the barrier metal layer, thereby filling the first contact hole, the second contact hole and the first trench, and partially filling the second trench, thereby forming a third trench; forming a void diffusion barrier layer on a portion of the first upper metal interconnection layer that has the third trench; forming a second upper metal interconnection layer on the void diffusion barrier layer, thereby filling the third trench; and dividing the first upper metal interconnection layer in the first trench from the first upper metal interconnection layer in the second trench and the second upper metal interconnection layer in the third trench by removing portions of the first upper metal interconnection layer, the void diffusion barrier layer, and the second upper metal interconnection layer.
Beneficially, the inter-metal dielectric layer is formed of a low dielectric constant material having a dielectric constant less than 3.
Beneficially, the first trench is narrower than the second trench.
Beneficially, the barrier metal layer is formed of at least one metal layer selected from a group consisting of a tantalum layer, a tantalum nitride layer, a titanium layer, and a titanium nitride layer.
Beneficially, the first upper metal interconnection layer is formed by an electroplating method.
Beneficially, the void diffusion barrier layer is formed of at least one material layer selected from a group consisting of a tantalum layer, a titanium layer, and an aluminum layer.
Beneficially, the void diffusion barrier layer is formed by using PVD, CVD, or ALD.
Beneficially, the portions of the first upper metal interconnection layer, the void diffusion barrier layer, and the second upper metal interconnection layer are removed by a CMP process.
Beneficially, the first and second upper metal interconnection layers comprise copper.
According to a still further aspect of the present invention, a method of forming a metal interconnection structure comprises: forming first and second lower metal interconnection layer patterns with a distance therebetween in a first inter-layer dielectric layer; forming an inter-metal dielectric layer on the first inter-layer dielectric layer and the first and second lower metal interconnection layer patterns; forming a first contact hole and a second contact hole that expose the first and second lower metal interconnection layer patterns, respectively, by removing a portion of the inter-metal dielectric layer; forming a barrier metal layer on exposed surfaces of the inter-metal dielectric layer and the first and second lower metal interconnection layer patterns; forming a metal layer on the barrier metal layer, thereby filling the first contact hole and the second contact hole, dividing the metal layer into a first via contact in the first contact hole and a second via contact in the second contact hole by planarization; forming a second inter-layer dielectric layer on the inter-metal dielectric layer, the first via contact, and the second via contact; forming a first trench and a second trench that expose portions of upper surfaces of the first via contact and the second via contact, respectively, by removing portions of the second inter-layer dielectric layer; forming a first upper metal interconnection layer that completely fills the first trench and fills a portion of the second trench, thereby forming a third trench therein; forming a void diffusion barrier layer on the first upper metal interconnection including the third trench, forming a second upper metal interconnection layer on the void diffusion barrier layer, filling the third trench, and dividing the first upper metal interconnection layer in the first trench from the first upper metal interconnection layer in the second trench and the second upper metal interconnection layer in the third trench by planarizing.